The present invention is directed to a method of setting armature/needle lift in a fuel injector by plastic deformation of a structural component of the fuel injector.
Fuel injectors are commonly employed in internal combustion engines to provide precise metering of fuel for introduction into each combustion chamber. Additionally, the fuel injector atomizes the fuel during injection, breaking the fuel into a large number of very small particles, increasing the surface area of the fuel being injected and allowing the oxidizer, typically ambient air, to more thoroughly mix with the fuel prior to combustion. The precise metering and atomization of the fuel reduces combustion emissions and increases the fuel efficiency of the engine.
An electro-magnetic fuel injector typically utilizes a solenoid assembly to supply an actuating force to a fuel metering valve. Typically, the fuel metering valve is a plunger style needle valve which reciprocates between a closed position, when the needle is seated in a valve seat along a sealing diameter to prevent fuel from escaping through a metering orifice disc into the combustion chamber, and an open position, where the needle is lifted from the valve seat, allowing fuel to discharge through the metering orifice for introduction into the combustion chamber.
Accurate lift set for the needle is important because the lift height affects the static flow of fuel through the injector. The previously known process of xe2x80x9cdirect lift setxe2x80x9d requires very accurate machines and metering components, and special geometry between a lower subassembly and an upper subassembly of the injector to form a xe2x80x9clockxe2x80x9d which holds the relative positions of the assemblies during connection of the subassemblies. The lower subassembly is generally comprised of a valve body, a seat/guide assembly, and an armature/needle assembly. The upper subassembly is generally comprised of a coil, an inlet tube, a housing, a non-magnetic shell, and a valve body shell.
The upper and lower subassemblies are pressed together to set the lift, with the interface occurring between the valve body and the valve body shell. This press involves shearing metal, causing a xe2x80x9cchipxe2x80x9d to shear off the valve body shell into a groove in the valve body. When attempting to push the two subassemblies together, the motion required to force the desired relationship is quite variable. For example, a 1000 Newton force may cause no motion, but a 1005 Newton force may cause the subassemblies to move 100 microns with respect to each other. It is seen, therefore, that control of the relative motions is difficult. For example, if the tooling used to set the lift pushes the subassemblies 20 microns closer together, the individual parts in each subassembly may compress some unknown amount, and the relative position of the parts may move some other, also unknown, amount. There is no absolute control of the relative positions of the parts, which makes direct lift setting a less than perfect process.
It would be beneficial to develop a method of setting lift height by a method that ensures producing the desired lift height.
Briefly, the present invention provides a method of setting a distance between a first body and a second body. The method comprises providing an intermediate body having a first end, a second end and a longitudinal axis, the first end being fixedly connected to the first body and the second end being fixedly connected to the second body; and compressing the intermediate body toward the longitudinal axis and axially elongating the intermediate body, the first body being separated from the second body.
Further, the present invention provides a method of setting armature/needle lift in a fuel injector. The method comprises providing a non-magnetic shell having a first end, a second end and a longitudinal axis; fixedly connecting the first end with a first subassembly; inserting an second subassembly into the second end, the second subassembly engaging the first subassembly; fixedly connecting the second subassembly to the non-magnetic shell; and compressing the non-magnetic shell toward the longitudinal axis and axially elongating the non-magnetic shell, the first subassembly being separated from the second subassembly.
Additionally, the present invention provides an armature/needle assembly lift setting apparatus. The apparatus comprises a plurality of punches. Each punch has a longitudinal axis intersecting at a common point and a contact end. The apparatus also includes an interior perimeter generally formed by the engagement ends of the plurality of punches. The interior perimeter is sized to accept a working piece therein, with the working piece including a working piece longitudinal axis. The apparatus also includes an actuator operatively connected to the plurality of punches such that operation of the actuator moves each of the plurality of punches along each respective longitudinal axis. The engagement end of each of the plurality of punches engages the working piece and compresses the working piece in a plane of the longitudinal axes and lengthens the working piece along the working piece longitudinal axis.
Additionally, the present invention provides a fuel injector comprising an upstream end body having an inlet tube, a downstream body having a valve body, and a longitudinal axis extending therethrough. The fuel injector also includes a hollow shell having a first end connected to the inlet tube, a second end connected to the valve body, and a central portion therebetween being plastically deformable toward the longitudinal axis, such that the hollow shell elongates along the longitudinal axis to separate the upstream end from the downstream end.